JP2004236178A - Image expansion device and electronic camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily reproduce a thumbnail image of a file recorded by another camera. <P>SOLUTION: This image expansion device has an expansion part for expanding compressed image data, a detection part, a calculation part, a replacement part and a transfer instruction part. The detection part detects an address of a start code indicating a staring position of an expanding operation of the image data in a memory. The calculation part calculates an address of a starting point of DMA transfer before the address of the start code. The replacement part replaces data between the start code and the starting point of DMA transfer in the memory with data for replacement. The transfer instruction part performs the DMA transfer of the data for replacement and the image data from the memory to the expansion part. Since reading of the data for replacement is skipped by the expansion part, it becomes equivalent to a fact that the leading address of SOI of the thumbnail image is transferred as the starting point of DMA transfer. Consequently, the thumbnail image of the file recorded by other camera can also be easily expanded. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image expansion device and an electronic camera including the image expansion device.
[0002]
[Prior art]
In an electronic camera, a photographed still image is often JPEG-compressed and recorded on a memory card. The structure of a JPEG file of a still image in Exif (Exchangeable Image File For Digital Still Camera) format used in most electronic cameras is as follows, for example.
[0003]
"SOI + APP1 + DQT + DHT + SOF + SOS + ECS + EOI"
SOI (Start of Image) is a marker code representing the beginning of a JPEG file. APP1 is an area for recording additional information specific to Exif format (including JPEG-compressed thumbnail image data). DQT is an area for recording the used quantization table. DHT is an area for recording a Huffman table used in Huffman coding. The SOF (Start of Frame) is an area for recording information indicating a JPEG compression mode and information such as a sampling ratio of image data. SOS (Start of Scan) is an area for recording scan information of image data. An ECS (Entropy Coded Segment) is an area for recording compressed main image data. EOI (End of Image) is a marker code representing the end of the JPEG file.
[0004]
Then, when the JPEG file (still image) recorded on the memory card is reproduced by the electronic camera, first, it is read into a memory such as a DRAM by an MPU (Micro Processor Unit). Next, the JPEG (compression) code stream corresponding to the main image in the file is input from the memory to the JPEG compression / decompression circuit by DMA (Direct Memory Access) transfer and subjected to decompression processing (decoding) (for example, , Patent Documents 1 and 2).
[0005]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 11-261887 (Section 4-10, FIG. 1-18)
[Patent Document 2]
JP-A-2001-61058 (Section 4-12, FIG. 1-18)
[0006]
[Problems to be solved by the invention]
Recently, a file format standard (such as Exif) and a file system standard (DCF: Design rule for Camera File system) of electronic cameras have been developed. For this reason, it is desired that a JPEG file photographed by another electronic camera can be reproduced at a higher speed.
[0007]
The main image of a JPEG file of a still image can be reproduced using DMA transfer when the file is temporarily read (stored) from a memory card into a memory and stored at an address convenient for the electronic camera.
On the other hand, a thumbnail image of a JPEG file of a still image is arranged at an address convenient for the electronic camera that has recorded the thumbnail image in the file. This address may be inconvenient for the electronic camera to be reproduced. For example, this is a case where the data size of one DMA transfer of the electronic camera on the recording side is smaller than that of the electronic camera on the reproduction side.
[0008]
In this case, if data is read from an address convenient for DMA transfer before the JPEG code stream of the thumbnail image, this data can be input to the JPEG compression / decompression circuit by DMA transfer. However, when the data placed before the JPEG code stream is arbitrary binary data, it does not necessarily mean that the data does not include the same code as the SOI. If it is included, JPEG decompression processing may not be performed normally. This is because the JPEG compression / decompression circuit starts JPEG decompression processing upon detecting SOI.
[0009]
Also, when a motion JPEG file (moving image) recorded by another electronic camera is reproduced, the JPEG decompression process may not be executed normally for the following two reasons. First, since the motion JPEG file must be reproduced at a predetermined frame rate, it is necessary to use high-speed DMA transfer. Second, motion JPEG files are recorded in a format such as QuickTime.
[0010]
More specifically, in the QuickTime format, a JPEG code stream corresponding to each frame of a moving image is recorded in a block called ATOM. Usually, another ATOM is also placed before the JPEG code stream corresponding to each frame. For this reason, the start address of the JPEG code stream corresponding to each frame is not always convenient for the DMA transfer of the electronic camera that reproduces it in the file. Therefore, as in the case of the thumbnail image, there is a possibility that the decompression process cannot be executed normally.
[0011]
It is an object of the present invention to provide a technique for easily reproducing a thumbnail image of a still image file, a moving image file, and the like recorded by another electronic camera using a conventional decompression circuit and DMA transfer.
[0012]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided an image decompression device including a decompression unit for decompressing compressed image data, a detection unit, a calculation unit, a replacement unit, and a transfer command unit. The detector detects a start code address indicating a start position of a decompression operation of the compressed image data in a memory storing the compressed image data. The calculation unit calculates the address of the start point of the DMA transfer preceding this address based on the address of the start code. The replacement unit replaces data between the address of the start code and the address of the start point of the DMA transfer in the memory with replacement data different from the start code. The transfer command unit causes the decompression unit to input the replacement data and the compressed image data stored in the memory by DMA transfer.
[0013]
According to a second aspect of the present invention, in the first aspect, the address of the start code detected by the detection unit is a resolution-reduced image (main image) in a file having main image data stored in the memory. This is the start position of the decompression operation of the compressed data (the image whose data resolution has been reduced). ].
According to a third aspect of the present invention, in the first aspect of the invention, the address of the start code detected by the detection unit is set to a value of the compressed image data of each frame in the moving image file stored in the memory. This is the start position of the extension operation. ].
[0014]
According to a fourth aspect of the present invention, in the image decompression apparatus according to any one of the first to third aspects, it is preferable that the replacing unit replaces the data to be replaced with the replacement data with another storage area in the memory before the replacement. After the replacement data is input to the decompression unit by the DMA transfer, the saved data is returned to the address before the save (between the address of the start code in the memory and the address of the start point of the DMA transfer). ].
[0015]
According to a fifth aspect of the invention, there is provided an electronic camera including an imaging unit, a recording unit, a memory, a data reading unit, and an image decompression device. The imaging unit captures an image of a subject and generates image data. The recording unit compresses the image data generated by the imaging unit and records the image data on a recording medium. The data reading unit reads out the image data recorded on the recording medium and stores it in the memory. The image decompression device is for decompressing image data stored in a memory.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<Configuration of this embodiment>
FIG. 1 is a block diagram of the electronic camera of the present invention. In the figure, an electronic camera 12 includes a photographing lens 16, a lens motor drive 20, a CCD (imaging device) 24, an A / D converter 28, a timing generator 32, a CCD interface 36, a system bus 38, A serial port 40, a parallel port 44, an image processing unit 48, a picture bus 50, a JPEG compression / decompression unit 52, a card interface 56, a USB (Universal Serial BUS) 60, a DMA controller 64, and a display controller 68, an MPU (Micro Processor Unit) 72, a bus interface 76, an LCD panel 80, an SDRAM 84, a ROM 88, and an I / O device 92 (for example, a JPEG2000 compression / decompression LSI). In addition, a memory card (recording medium) 96 is connected to the electronic camera 12.
[0017]
The MPU 72 controls the system of the electronic camera 12 via the system bus 38.
The DMA controller 64 controls the DMA transfer according to a command from the MPU 72.
The SDRAM 84 is controlled by an SDRAM controller (not shown).
The electronic camera 12 of the present embodiment is the same as a conventional electronic camera except that the function of the MPU 72 is different as described later. Therefore, the description of the other units will be omitted.
[0018]
<Description of the operation of the present embodiment>
FIG. 2 is a flowchart showing an image expansion operation by the electronic camera 12 described above. Hereinafter, the operation of image decompression will be described according to the step numbers shown in the figure. In the following description, it is assumed that a JPEG file recorded by another electronic camera is stored in the memory card 96, and only the operation of reproducing the JPEG file will be described.
[0019]
[Step S1]
The MPU 72 reads the JPEG file recorded on the memory card 96 and stores it in the SDRAM 84. The JPEG file may be read out by DMA transfer using the DMA controller 64 and stored in the SDRAM 84. At this time, the MPU 72 stores the address at which the SOI of the JPEG file in the SDRAM 84 is the start point of the DMA transfer. The start point of the DMA transfer here is, for example, the head position of the page of the SDRAM 84.
This operation is the same when reproducing a JPEG file of a still image in the Exif format or the like and in reproducing a JPEG file of a moving image in the QuickTime format or the like.
[0020]
[Step S2]
The MPU 72 determines whether the JPEG file stored in the SDRAM 84 is a still image file or a moving image file. If it is a still image file, the process proceeds to step S3. If it is a moving image file, the process proceeds to step S10.
[0021]
[Step S3]
When the thumbnail image is expanded, the process proceeds to step S5. When the main image is expanded, the process proceeds to step S4.
[0022]
[Step S4]
The MPU 72 instructs the DMA controller 64 to DMA-transfer the JPEG file to the JPEG compression / decompression unit 52 in order from the leading data. The DMA controller 64 DMA-transfers the JPEG file from the SDRAM 84 via the bus interface 76 and the picture bus 50 to the JPEG compression / decompression unit 52 (starting from the SOI as described in step S1).
In general, a JPEG compression / decompression unit of an electronic camera is configured to start JPEG decompression processing from that point when an SOI marker code is detected from data input from a compression code input / output port (not shown). ing. Therefore, the JPEG compression / decompression unit 52 executes the JPEG decompression processing from the time when the head (SOI marker code) of the DMA-transferred data is detected. Thus, the JPEG expansion of the main image is completed.
[0023]
[Step S5]
The MPU 72 searches for a marker code of SOI and a marker code of APP1 in the JPEG file.
[Step S6]
The MPU 72 reads the Exif attached information, and obtains the start address of the SOI of the thumbnail image (JPEG format) stored in the application segment (APP1 segment) in the JPEG file and the size of the JPEG code stream of the thumbnail image.
[0024]
[Step S7]
The MPU 72 obtains the address of the nearest DMA transfer start point by tracing back from the SOI address of the thumbnail image. The MPU 72 saves the data between the SOI of the thumbnail image and the start point of the DMA transfer in another area of the SDRAM 84. The different area here is an area different from the area in which the JPEG file is stored in the SDRAM 84, and it is desirable to provide an area dedicated to save data in advance.
[0025]
[Step S8]
The MPU 72 replaces all data between the SOI of the thumbnail image and the start point of the DMA transfer with “replacement data”. The “replacement data” is preferably a code that is easily distinguishable, for example, “00h” or “FFh”, but may be anything other than the marker code (“FFD8h”) of the SOI of the JPEG file.
[0026]
FIG. 3 shows an area storing a thumbnail image in a JPEG file in the SDRAM 84 after the above-described data replacement is performed. The padding data in the figure is dummy data added between the EOI and the end point of the DMA transfer by the DMA transfer during the JPEG expansion process by the JPEG compression / expansion unit 52. When detecting the EOI marker code from the data input from the compression code input / output port (not shown), the JPEG compression / decompression unit 52 stops (ends) the JPEG decompression process. Therefore, the dummy data described above does not affect the JPEG decompression processing of the JPEG compression / decompression unit 52.
[0027]
As shown, in the SDRAM 84, the SOI address of the thumbnail image (of the JPEG file recorded by another camera) is often different from the start point of the DMA transfer of the electronic camera 12 that reproduces the thumbnail image.
Since the data to be replaced remains in the memory card, there is little problem even if the data to be replaced is not saved in step S7. Even if such data is saved, the image reproduction speed hardly decreases. This is because the number of bytes to be replaced is at least smaller than the number of bytes for one DMA transfer, and may be about several tens of bytes.
[0028]
[Step S9]
The MPU 72 causes the JPEG compression / decompression unit 52 to input the JPEG code stream including the replaced data (replacement data) by DMA transfer in the same manner as in the case of the main image.
The JPEG compression / decompression unit 52 skips all replacement data. This is because the replacement data does not include the SOI marker code. This is equivalent to performing DMA transfer to the JPEG compression / decompression unit 52 using the start address of the SOI of the thumbnail image as the start point of DMA transfer. Therefore, the JPEG compression / decompression unit 52 normally decompresses the thumbnail image by JPEG.
[0029]
After the replacement data is input to the JPEG compression / decompression unit 52, the MPU 72 returns the saved data to the address before saving (between the SOI of the thumbnail image in the SDRAM 84 and the start point of the DMA transfer). . Thus, the JPEG decompression operation of the thumbnail image is completed.
[0030]
[Step S10]
The MPU 72 searches for the head position of ATOM in the JPEG file of the moving image. Next, the MPU 72 checks the head address of the JPEG code stream corresponding to each frame (frame) of the moving image for each frame (the head address of each frame can be detected from the file header information).
[0031]
[Step S11]
If the start address of each frame is different from the address of the start point of the DMA transfer, the MPU 72 traces forward from the start address of each frame to find the address of the closest start point of the DMA transfer. Then, the MPU 72 replaces the data between the start address of the JPEG code stream of each moving image frame and the start point of the DMA transfer with the replacement data.
[0032]
In the case where a JPEG file of a moving image is played back at a normal speed in the order of time, it is desirable not to perform the saving operation of the replaced data described in step S7. There are three reasons.
First, it is necessary to reproduce the JPEG code stream of each frame without delay according to the determined frame rate. For this reason, it is desirable not to perform an operation that requires extra time.
Second, in the case of a moving image JPEG file, important data is rarely placed between frames, and it is considered that there is no problem even if such data is replaced. There is a possibility that the last data of the previous frame may be replaced, but since the previous frame has already been reproduced, the data may be replaced.
Third, the JPEG file to be played remains on the memory card 96.
[0033]
[Step S12]
As in step S9, the MPU 72 causes the JPEG compression / decompression unit 52 to input the JPEG code stream of each frame of the moving image by DMA transfer.
The JPEG compression / decompression unit 52 skips all replacement data. Therefore, for the same reason as in step S9, each frame image of the moving image is normally JPEG expanded. Thus, the operation of decompressing the moving image JPEG file is completed.
[0034]
<Effect of this embodiment>
In the present embodiment, when playing back a thumbnail image in a JPEG file of a still image, the MPU 72 converts the data between the SOI of the thumbnail image and the start point of the DMA transfer into data that is skipped by the JPEG compression / decompression unit 52. Replace with Thereafter, the JPEG code stream of the thumbnail image together with the replaced data is DMA-transferred to the JPEG compression / decompression unit 52. Therefore, even if the JPEG file is recorded by another camera, the thumbnail image in the JPEG file can be JPEG-decompressed at high speed and normally by using the DMA transfer.
[0035]
Also in the case of reproducing a moving image JPEG file, the MPU 72 replaces the data between the start point of the decompression operation of each frame and the start point of the DMA transfer, as described above. Accordingly, JPEG files of moving images recorded by other cameras can be JPEG-decompressed at high speed and normally using DMA transfer.
As described above, the JPEG file recorded by another camera can be normally and easily reproduced, so that compatibility between the cameras can be improved. As a result, user convenience can be improved.
[0036]
In addition, the decompression operation of the present embodiment can reproduce the entire JPEG code stream at a higher speed than a method of moving the decompression operation start point address to the DMA transfer start point address. This is because the number of bytes of data replaced by the decompression operation of the present embodiment is smaller than the number of bytes of the entire JPEG code stream (step S8).
[0037]
The main difference from the conventional JPEG file playback operation is that the data between the start point of the decompression operation of the thumbnail image (or each frame of the moving image) and the start point of the DMA transfer is replaced before the DMA transfer. . Therefore, the decompression processing of the present embodiment can be realized only by changing the function (software processing) of the MPU 72. One unit (data size) of data transfer in the DMA transfer is not limited. Therefore, regardless of the number of bytes of one DMA transfer which is unique to the camera, it can be easily implemented in a conventional electronic camera. That is, since the components of the electronic camera 12 including the JPEG compression / decompression unit 52 may be the same as those in the related art, no extra cost is required.
[0038]
Generally, thumbnail images are often read from a large number of JPEG files and displayed in a list, and high-speed playback is required. In such a case, if the decompression operation of the present embodiment is applied, normal and high-speed decompression can be performed, so that user convenience can be greatly improved.
In recent digital cameras, in order to improve the response at the time of reproduction, an image for monitor display (an image having a size suitable for display on a monitor screen) is JPEG-compressed and recorded in a unique area of the APP1 segment. is there. Also in the case of reproducing (expanding) such an image for monitor display, the decompression operation of the present embodiment can be used. Since the monitor display image is generally larger than the thumbnail image, the effect of the high-speed JPEG decompression by the DMA transfer is greater.
[0039]
<Supplementary information of this embodiment>
[1] In the present embodiment, an example of reproducing a JPEG file has been described. The present invention is not limited to such an embodiment. The present invention can be applied to the case of playing back a file of another format such as JPEG2000. Also in this case, if the data between the start point of the image data decompression operation and the start point of the DMA transfer is replaced with data skipped by the decompression circuit before the DMA transfer, normal reproduction can be performed.
[0040]
[2] In the case of reproducing a thumbnail image of a still image file, as described in step S7, an example has been described in which data to be replaced is saved. The present invention is not limited to such an embodiment. It is not necessary to evacuate. This is because the still image file remains in the memory card 96.
[0041]
[3] An example has been described in which, when a moving image file is played back at a normal speed in time sequence, replaced data is not saved. The present invention is not limited to such an embodiment. You may be evacuated.
However, when rewinding and playing back a moving image file, it is desirable to perform a save / restore operation as in steps S7 and S9. This is because, in the rewind reproduction, it is considered that the frame is reproduced from the frame transferred later in time. That is, since the frame immediately before (the one closer to the beginning of the file) is reproduced next to the frame being reproduced, the data of the immediately preceding frame must not be lost.
[0042]
For the same reason, it is desirable to perform the save / restore operation even when the moving image file is repeatedly reproduced.
In the case of high-speed rewind reproduction, it is desirable not to perform the save / restore operation. This is because, since the immediately preceding frame is not reproduced, there is no problem if the data is lost, so that it is better not to spend extra time and memory in the save / restore operation.
[0043]
<Correspondence with Claims>
Finally, the correspondence between the claims and the present embodiment will be described. In addition, the following correspondence is an interpretation shown for reference, and does not limit the present invention.
[0044]
The memory described in the claims corresponds to the SDRAM 84.
The decompression unit described in claims corresponds to the function of the JPEG compression / decompression unit 52 for decompressing the compressed image data (see steps S4, S9, and S12).
The address of the start code described in the claims corresponds to the SOI of the JPEG file detected in step S5, the SOI of the thumbnail image detected in step S6, and the start address of the JPEG code stream corresponding to each frame detected in step S10. .
[0045]
The detection unit described in claims corresponds to the function of the MPU 72 that detects the address of the start code.
The calculating unit described in claims corresponds to the function of the MPU 72 that calculates the DMA transfer start point before the address based on the address of the start code (see steps S7 and S11).
[0046]
The replacement unit corresponds to the function of the MPU 72 that replaces data between the SOI of the thumbnail image and the start point of the DMA transfer with replacement data (see step S8).
The transfer command section described in the claims corresponds to the functions of the MPU 72 and the DMA controller 64 for inputting the JPEG code stream to the JPEG compression / decompression section 52 by DMA transfer (see steps S4, S9, and S12).
[0047]
The reduced resolution image described in the claims corresponds to a thumbnail image and a monitor display image.
The image decompression device according to the present invention has a function of the MPU 72 and the DMA controller 64 as the detection unit, the calculation unit, the replacement unit, and the transfer command unit, and a function of the JPEG compression / decompression unit 52 for decompressing the compressed image data. Corresponding to
[0048]
The imaging unit described in claims corresponds to the photographing lens 16, the lens motor drive 20, the CCD 24, the A / D conversion unit 28, the CCD interface 36, and the image processing unit 48. The operation of “image a subject and generate image data” described in the claims is well-known, and thus the description is omitted.
The recording unit described in the claims corresponds to the function of the MPU 72 that causes the JPEG compression / decompression unit 52 to compress image data and record the compressed image data on the memory card 96. Since this operation is also known, the description is omitted.
[0049]
The data reading unit described in the claims corresponds to the function of the MPU 72 that reads a JPEG file recorded on the memory card 96 and stores the JPEG file in the SDRAM 84, and the SDRAM 84 (see step S1).
[0050]
【The invention's effect】
According to the present invention, when a resolution-reduced image in a still image file is reproduced, data between the start point of the decompression operation of the compressed data of the resolution-reduced image and the start point of the DMA transfer is read by the decompression unit. Replace with Thereafter, the compressed data of the reduced-resolution image together with the replaced data is DMA-transferred to the decompression unit. Therefore, even if the still image file is recorded by another camera, the reduced resolution image therein can be normally and easily reproduced by the decompression unit.
[0051]
Also in the case of reproducing a moving image file, the data between the start point of the decompression operation of each frame and the start point of the DMA transfer is replaced in the same manner as described above. Therefore, a moving image file recorded by another camera can be normally and easily reproduced.
[Brief description of the drawings]
FIG. 1 is a block diagram of an electronic camera according to the present invention.
FIG. 2 is a flowchart showing an image expansion operation by the electronic camera of the present invention.
FIG. 3 is an explanatory diagram showing an area storing a thumbnail image in a JPEG file in the SDRAM after data replacement is performed.
[Explanation of symbols]
12 electronic camera 16 shooting lens 20 lens motor drive 24 CCD
28 A / D conversion unit 28
32 timing generator 36 CCD interface 38 system bus 40 serial port 44 parallel port 48 image processing unit 50 picture bus 52 JPEG compression / decompression unit 56 card interface 60 USB
64 DMA controller 68 Display controller 72 MPU
76 Bus interface 80 LCD panel 84 SDRAM
88 ROM
92 I / O device 96 Memory card

Claims (5)

A decompression unit for decompressing the compressed image data;
A detection unit that detects an address of a start code indicating a start position of a decompression operation of the compressed image data in a memory that stores the compressed image data;
A calculating unit that calculates an address of a start point of the DMA transfer before the address based on an address of the start code;
A replacement unit that replaces data between the address of the start code and the address of the start point in the memory with replacement data different from the start code;
An image decompression device, comprising: a transfer command unit that inputs the replacement data and the compressed image data stored in the memory to the decompression unit by the DMA transfer. The image decompression device according to claim 1,
The address of the start code detected by the detection unit is used for expanding the compressed data of the reduced-resolution image (the image obtained by reducing the resolution of the main image data) in the file having the main image data stored in the memory. An image decompression device, which is a start position. The image decompression device according to claim 1,
An image decompression device, wherein the address of the start code detected by the detection unit is a start position of a decompression operation of decompressed image data of each frame in a moving image file stored in the memory. The image decompression device according to any one of claims 1 to 3,
The replacement unit,
The data to be replaced with the replacement data is evacuated to another storage area in the memory before the replacement,
After the replacement data is input to the decompression unit by the DMA transfer, the saved data is returned to the address before saving (between the address of the start code and the address of the start point in the memory). An image decompression device characterized by the above-mentioned. An imaging unit that images a subject and generates image data;
A recording unit that compresses the image data generated by the imaging unit and records it on a recording medium;
A data reading unit that has a memory and reads image data recorded on the recording medium and stores the image data in the memory;
5. An electronic camera, comprising: the image decompression device according to claim 1, which decompresses image data stored in the memory.

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